The broad, long-term objective of the proposed project is to contribute to the development and validation of children's mental health services that are clinically and cost-effective at reducing behavioral and emotional disturbance. The specific aims are: (a) Using an independent research team, evaluate the clinical- and cost-effectiveness of a promising services package, Multi-Systemic Therapy (MST) which has not yet been independently evaluated; (b) evaluate the effectiveness of MST for a population that typically fails to receive needed mental health services: behaviorally disordered, pre-adjudicated adolescents from low income backgrounds; (c) evaluate the effectiveness of MST for behaviorally disturbed females, who represent an important but under-studied population; and (d) evaluate the impact of potential "investigator allegiance effects", which some researchers suggest may influence the results of treatment outcome studies, on the evaluation of MST. Project participants will be 240 junior high school and high school students (and their families) enrolled in public school Moderate Intervention Program (MIP) classrooms. MIP classrooms are designed for students with serious behavior problems, whose behavior cannot be managed in regular classrooms. These classrooms provide a behaviorally programmed classroom, a low student / teacher ratio, and on occasion, traditional counseling services. Most students in these classrooms are from low income backgrounds, and fail to receive any mental health services. Half of the 240 participant students (representing the control group) will be randomly assigned to receive regular MIP classroom services, provided by the school system; half will in addition receive MST services, provided by the project. MST training and backup supervision will be provided by the developers of MST, but all other aspects of the project will be conducted independently of the developers. Participants will be assessed at four time points, including a one year follow-up. Assessments will focus on: (1) the individual functioning of parent and child; 2) family relations; 3) peer relations; 4) involvement with the legal system; and 5) cost-effectiveness data.